types: Make bool generally available

Add an include on stdbool.h, making the bool type generally available
within the GRUB without needing to add a file-specific include every
time it would be used.

Signed-off-by: Robbie Harwood <rharwood@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

grub-core/commands/parttool.c

@@ -315,7 +315,7 @@ grub_cmd_parttool (grub_command_t cmd __attribute__ ((unused)),
 		    switch (curarg->type)
 		      {
 		      case GRUB_PARTTOOL_ARG_BOOL:
-			pargs[curarg - ptool->args].bool
+			pargs[curarg - ptool->args].b
 			  = (args[j][grub_strlen (curarg->name)] != '-');
 			break;